an aerodynamic three wheeled automobile (the dart) runs on a compressed natural gas stored in two cylinders in the rear of the vehicle. the 13,000 dart can cruise at speeds up to 70 miles per hour and it can travel 105 miles per gallon of fuel. another two seater automobile costs 12000 and average 5t miles per gallon of compressed natural gas. if girl costs $8.50 per gallon and Marr is 12% per year , over what range of annual miles driven is the dart more economical? assume a useful life of four years for both cars.